Kinetic Isotope Effects in the Radiation-induced Oxidation of Alcohols by Hydrogen Peroxide in Aqueous Solution

1971 ◽  
Vol 49 (8) ◽  
pp. 1305-1309 ◽  
Author(s):  
C. E. Burchill ◽  
G. F. Thompson
Keyword(s):  
Hydrogen Peroxide ◽  
Kinetic Isotope Effect ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chain Oxidation ◽  
Oxidation Of Methanol ◽  
Kinetic Isotope ◽  
Oxidation Of Alcohols ◽  
Radiation Induced

By using selectively deuterated alcohols it is demonstrated that abstractions from both α and β positions of 2-propanol and ethanol contribute to the overall mechanism for the radiation-induced chain oxidation of these alcohols by hydrogen peroxide. Kinetic isotope effects are measured for abstraction of H by OH from 2-propanol and ethanol at both α and β positions and for the H atom transfer reaction from the alcohol to the β radical. The chain oxidation of methanol shows no primary kinetic isotope effect on substitution of CD3OH.

scholarly journals Horseradish peroxidase. XXIX. Reactions in water and deuterium oxide: cyanide binding, compound I formation, and reactions of compounds I and II with ferrocyanide

1978 ◽  
Vol 56 (22) ◽  
pp. 2844-2852 ◽  
Author(s):  
H. Brian Dunford ◽  
W. Donald Hewson ◽  
Håkan Steiner
Keyword(s):  
Hydrogen Peroxide ◽  
Horseradish Peroxidase ◽  
Kinetic Isotope Effect ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Compound I ◽  
Kinetic Isotope ◽  
Cyanide Binding ◽  
Compound Ii

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKa of 5.2 for compound I and for compound II a pKa of 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positive kH/kD values possess a labile proton.

SOME DEUTERIUM KINETIC ISOTOPE EFFECTS: IV. β-DEUTERIUM EFFECTS IN WATER SOLVOLYSIS OF ETHYL, ISOPROPYL, AND tert-BUTYL COMPOUNDS

1960 ◽  
Vol 38 (11) ◽  
pp. 2171-2177 ◽  
Author(s):  
K. T. Leffek ◽  
J. A. Llewellyn ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Alkyl Halides ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Intramolecular Forces

The secondary β-deuterium isotope effects have been measured in the water solvolytic reaction of alkyl halides and sulphonates for primary, secondary, and tertiary species. In every case the kinetic isotope effect was greater than unity (kH/kD > 1). This isotope effect may be associated with varying degrees of hyperconjugation or altered non-bonding intramolecular forces. The experiments make it difficult to decide which effect is most important.

Solvolysis of specifically deuterated 7-chloro- and 7-bromo-exo-2-norbornyl brosylates; unusually large γ-kinetic isotope effects in the absence of σ-participation

1980 ◽  
Vol 58 (16) ◽  
pp. 1738-1750 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
George Timmins ◽  
Frank Peter Cappelli
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

A series of specifically deuterated syn-7-chloro-, anti-7-chloro-, syn-7-bromo-, and anti-7-bromo-exo-2-norbornyl brosylates have been prepared and solvolyzed in NaOAc-buffered 80:20 EtOH–H2O. For solvolysis at 25 °C the γ-kinetic isotope effects (KIE's) for syn-7-chloro-exo-2-norbornyl brosylate-endo-6-d (1e), anti-7-chloro-exo-2-norbornyl brosylate-endo-6-d (2c), syn-7-bromo-exo-2-norbornyl brosylate-endo-6-d (1f), anti-7-bromo-exo-2-norbornyl brosylate-endo-6-d (2d), syn-7-chloro-exo-2-norbornyl brosylate-exo,exo-5,6-d2 (1g), anti-7-chloro-exo-2-norbornyl brosylate-exo,exo-5,6-d2 (2e) are 1.125 ± 0.007, 1.128 ± 0.005, 1.063 ± 0.008, 1.149 ± 0.020, 1.119 ± 0.011, and 1.115 ± 0.013, respectively. There is no detectable γ-kinetic isotope effect for solvolysis of anti-7-chloro-endo-2-norbornyl brosylate-endo-6-d(3a) and the β-KIE for anti-7-chloro-exo-2-norbornyl brosylate-exo-3-d(4a) is 1.111 ± 0.011. From a consideration of the possible sources of the unusually large secondary KIE's, we conclude that the exo-6-d and endo-6-d γ-KIE's likely are derived from a combination of effects rather than from participation of the C1—C6 bond in the ionization step.

Arrhenius-Parameter und kinetischer Isotopeneffekt für die Reaktion von Wasserstoffatomen mit Silan

1974 ◽  
Vol 29 (3) ◽  
pp. 493-496 ◽  
Author(s):  
Peter Potzinger ◽  
Louis C. Glasgow ◽  
Bruno Reimann
Keyword(s):  
Kinetic Isotope Effect ◽  
Relative Rate ◽  
Isotope Effects ◽  
Preexponential Factor ◽  
Kinetic Isotope Effects ◽  
Hydrogen Atoms ◽  
Kinetic Isotope ◽  
Abstraction Reaction ◽  
Upper Limits ◽  
Relative Rate Constants

The Reaction of Hydrogen Atoms with Silane; Arrhenius Parameters and Kinetic Isotope Effect Relative rate constants were measured for the systems H + C2H4/SiD4 and D + C2D4/SiH4 over a wide temperature range. From the known arrheniusparameter for the reaction H + C2H4 the activation energy EA and the preexponential factor A of the abstraction reactionH + SiD4 → HD + SiD3may be calculated. Values of EA = 3.2 kcal/Mol and A = 4.92 • 1013 cm3 Mol-1 sec-1 were obtained. Upper limits for the kinetic isotope effects are given in the paper

Transition-state structure for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride

2015 ◽  
Vol 93 (4) ◽  
pp. 463-467 ◽  
Author(s):  
Jefferson Chan ◽  
Ariel Tang ◽  
Andrew J. Bennet
Keyword(s):  
Transition State ◽  
Kinetic Isotope Effect ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Theoretical Modelling ◽  
Kinetic Isotope ◽  
Hydronium Ion ◽  
Anomeric Carbon ◽  
Hydrolysis Of

The transition state for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride in water has been characterized by combining multiple kinetic isotope effect measurements with theoretical modelling. The measured kinetic isotope effects for the C1-deuterium, C2-deuterium, C5-deuterium, anomeric carbon-13, and ring oxygen-18 are 1.219 ± 0.021, 1.099 ± 0.024, 0.976 ± 0.014, 1.014 ± 0.005, and 0.991 ± 0.013, respectively. The transition state for the hydronium ion reaction is late with respect to both C–F bond cleavage and proton transfer.

Radiation-induced Oxidation of 2-Propanol by Nitrous Oxide in Alkaline Aqueous Solution

1972 ◽  
Vol 50 (11) ◽  
pp. 1751-1756 ◽  
Author(s):  
C. E. Burchill ◽  
G. P. Wollner
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Kinetic Isotope ◽  
Alkaline Aqueous Solution ◽  
Radiation Induced ◽  
Solution Proceeds

The radiation-induced oxidation of 2-propanol to acetone by N2O in alkaline aqueous solution proceeds via a free radical chain mechanism independent of pH above 12.5. The results are explained by abstraction of H from 2-propanol by O− at both the α and β positions (85% α attack). Chain propagation is by reaction of the α radical anion, (CH3)2ĊO−, with N2O with a rate constant of (3.8 ± 0.4) × 104 M−1 s−1 and by reaction of the β radical, ĊH2(CH3)CHOH, with 2-propanol to give the α radical with a rate constant of 430 ± 30 M−1 s−1.The conclusions are supported by the demonstration of kinetic isotope effects for selectively deuterated alcohols.

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